To understand the function of a draw wire displacement sensor, you first need to grasp how it works—it’s actually similar to using a tape measure to measure length in everyday life, except that it has been upgraded with intelligent features such as “automatic measurement and data transmission.”

The core structure of the sensor consists of four components: the cable, the pulley, the return spring, and the encoder:

Mechanical linkage: One end of the pull cord is secured to the lift’s movable platform via a mounting bracket, while the other end is wound around the internal hub; the hub is connected to a return spring, which automatically retracts the pull cord after it extends, keeping it taut at all times;

Motion conversion: When the lift platform rises, it pulls the cord, causing the hub to rotate clockwise; when the platform descends, the return spring pulls the hub to rotate counterclockwise, retracting the cable;

Signal Output: The hub is coaxially connected to the encoder; the rotation of the hub drives the encoder shaft to rotate; the encoder converts the “mechanical rotation” into an “electrical signal” (such as a 4-20mA analog signal, RS485 digital signal, etc.) by detecting the angle of rotation of the shaft ;

Data Application: The electrical signal is transmitted to the lift controller. By calculating changes in the electrical signal, the controller determines the real-time height of the lifting platform and controls its operation according to preset instructions.

Simply put, the draw wire displacement sensor acts as the “eyes” of the lift, converting physical information—such as “how high the platform has risen or how far it has descended”—into digital signals that the controller can “understand,” thereby enabling precise control.